I have a 2015 IS250 AWD. I love it and have been pleased. I have noticed an odd steering issue that seems to be problematic in the previous generations, and it concerns me because it only has 70k miles on it and it could be rather dangerous. It does not happen on the interstate on my drive to work because I am only going roughly 8 miles around 80 mph. However, when I drive over 15 minutes or so at that speed the steering column begins to get stuck in the center. When the road turns or you need to steer slightly in either direction the car sort of over corrects into whichever direction you steer which can be a rather uneasy feeling. I'm assuming the issue occurs once everything is good and hot. I have only experienced it 3 times since I rarely go out of town. I noticed that wiggling the steering wheel slightly can make it go away - temporarily (or I slow down to about 70). I have read some threads where people describe it as a "notch" feel.

There was a service bulletin I found in another thread that seems very similar to my issue- L-SB-0016-11. I read where people have replaced the power steering gear assembly or reset the ECU. I am a two hour drive from the Lexus dealership and I do routine maintenance myself. I was hoping for some suggestions before taking it in - I don't trust many mechanics.

Thank you!

 

Welcome to the forum!

In review of the TSB you mentioned it appears it only effected 2WD (RWD) vehicles and the issue was corrected during 2010 IS production.
It's not to say your car could not be experiencing a similar scenario, but the likelihood of it being the condition in the TSB is very, very slim.
Also you will note in the description they mention the condition as occurring after making a steering maneuver and the steering doesn't want to center…"Some Lexus vehicles may exhibit an intermittent non-binding, notchy steering feel and/or the steering wheel will not smoothly self-center when driving at highway speeds. This condition may occur when changing lanes or when coming out of long sweeping turns at highway speeds."
Obviously they aren't going to go into really specific detail, but it seems like your concern is happening before you make the steering maneuver.

Given the age of your vehicle, and not knowing when the alignment was done, I would first suggest checking tires for even wear, adjusting all tires pressures so they are correct, getting an alignment done, and most importantly, item #6 at the end of the same TSB...
"6. Initialize the rotation angle sensor and calibrate the torque sensor zero point."
Typically techs do not perform item #6 above after and alignment, and it's so important they do...or you then start to have wandering (or other issues) at highway speeds...some similar to what you describe.
The dealer may suggest that item #6 above only needs to be done when removing/replacing parts (like a steering rack), but if they actually open the repair manual it clearly states to perform these procedures after an alignment, regardless if parts were replaced/removed.

 

I have a very similar issue, 2012 is250 rwd. Steering gets notchy after driving highway speeds for about 15 min. It's been aligned, calibrated. I poked around at the connectors on the ecu and rack didn't see anything obvious.